This project is focused on the study of the pathogenesis of HIV-associated malignancies and the development of novel therapies for these tumors based on this understanding. Much of the work on AIDS-related malignancies has focused on tumors associated with Kaposis sarcoma-associated herpesvirus (KSHV), also called human herpesvirus-8 (HHV-8). This virus is the cause of Kaposis sarcoma (KS), primary effusion lymphoma (PEL) and multicentric Castlemans disease (MCD), tumors that most frequently occur in HIV-infected patients. We have found that hypoxia can activate latent KSHV to undergo lytic replication and that several genes of KSHV are specifically upregulated by hypoxia. We had previously found that a gene of unknown function, ORF34, is specifically activated by hypoxia. ORF34 is part of a cluster of genes (ORF34 to 37) that are all similarly upregulated. We have dissected the molecular structure of this gene cluster and its upregulation by hypoxia. One of these genes, ORF36, can phosphorylate ganciclovir, and activation of this gene by hypoxia can be able to be used to therapeutic benefit in KSHV-associated tumors and conditions, especially PEL and MCD. More recently, we have shown that KSHV latency-associated nuclear antigen (LANA) is upregulated by hypoxia. In addition, we have found that a KSHV-encoded thymidine kinase (ORF21) is upregulated in KSHV-infected cells exposed to hypoxia. This gene can phosphorylate zidovudine (AZT) to a form that is toxic for cells. We are currently exploring the interplay between hypoxia and other KSHV genes and in addition, the effects of hypoxia on KSHV-infected cells. We are also comparing the effects of hypoxia and the hypoxia-inducible factors (HIF-1 and HIF-2) on KSHV and cellular genes. Expanding on the observation that hypoxia upregulates ORF36 and ORF21, we have found that phosphorylation of ganciclovir and AZT is increased in PEL cells exposed to hypoxia and that clinically attainable concentrations of these drugs can kill the PEL cells. This approach could be used as a basis to treat either PEL (which develops in a hypoxic environment) or MCD (in which KSHV lytic genes are already activated), and we recently shown that these two drugs can be used to treat KSHV-MCD. We are also exploring other approaches to the treatment of KSHV-associated malignancies, including pomalidomide and related cereblon-binding thalidomide analogs. We are investigating the effect of these drugs on KSHV-infected cells and the biochemical mechanisms for any effects. In particular, we are studying the effects of these drugs on the MHC-1 downregulation that is caused by KSHV infection. We have found that LANA has varying effects on the regulation of various human genes by HIF. More recently, we are exploring how XBP-1 regulates specific KSHV genes, and have found that it can directly upregulate KSHV-encoded viral interleukin-6 (vIL-6). This may be important for the pathogenesis of KSHV-induced MCD. We have also been exploring how KSHV infection and hypoxia interact to affect the cellular miRNA in KSHV-infected cells and the functional effects of these interactions. KSHV can induce HIF, and we are also exploring the effects of HIF-knockdown on various functions in PEL cells. We are also exploring the effects of various stimuli on KSHV-encoded miRNA. Finally, we are conducting laboratory studies to assess the levels of cytokines and other factors in patients on clinical trials for AIDS malignancies. We have identified a group of patients with KSHV infection but without MCD who have systemic inflammatory symptoms similar to that of MCD and who have high serum levels of KSHV-encoded viral interleukin-6 (vIL-6). This represents a new disease entity of KSHV interleukin-6 cytokine syndrome (KICS).